potential health hazards associated with exposure to extremely low epidemiological studies that suggest a link between exposure to 60 Hz certain types of human cancers. However, a scientific answer to this question is not yet available because the molecular mechanisms that mediate cellular interactions with EMF are just beginning to be elucidated. The proposed experiments utilize Saccharomyces cerevisiae (yeast) as an eukaryotic model system because it provides elegant genetic and molecular cloning approaches that are not available for other types of cells. Specifically, they are interested in the molecular basis whereby 60 Hz EMF affect the expression of specific genes, presumably at the level of transcription. This biological phenomenon was first reported by Weisbrot et al. Toward further understanding of the molecular processes that mediate these effects on gene expression, they have three specific aims: 1) To rigorously replicate the published experiments cited above. These investigators reported that expression of two genes the SSA1 heat shock gene and URA3, a gene involved in nucleotide metabolism - is induced within 15-20 minutes on exposure of yeast to 60 Hz EMF. Then, within less than 60 minutes, transcript levels for both genes return to control levels; 2) To extend the investigation of these published experiments by examining how the molecular response is affected by the introduction of additional exposure parameters. For example, they will modify the published protocol by removing the mu-metal shielding without affecting the incubation conditions of the cells. This will allow them to evaluate directly whether exposure to any weak stray AC fields and the earth's magnetic fields alters the biological response observed when the cells were maintained within the Mu-metal chamber; and 3) To determine whether any of EMF-exposure parameters that influence transcriptional activity during short term EMF exposure also mediate this bioeffect during the longer exposure periods used in their yeast EMF-exposure protocol. Insight into the mechanism of action in yeast will shed light on the molecular basis of the responses that have been observed in more complex eukaryotic organisms. Thus, these studies will help fill the gap in their knowledge to evaluate more critically whether exposure to 60 Hz EMF present a health hazard to humans.